The present invention is based on a method for supervising the connections of a transmission system and on devices for carrying out the method.
For networked information systems, in particular in a motor vehicle, components such as, for example, navigation units, CD changers, or a telephone are utilized in addition to a control unit (for example the conventional car radio). In complex networked systems, there is generally a need to specify suitable methods for smooth communication among all components. The communication system is separate from the actual application, and possesses, for example, a structure according to the ISO""s OSI model.
European Patent No. 511 794 describes a system in which one designated station (xe2x80x9cmasterxe2x80x9d) establishes and terminates the connection to the other stations (xe2x80x9cslavesxe2x80x9d). Following its activation or after a reset, the xe2x80x9cmasterxe2x80x9d uses a signal to request all the xe2x80x9cslavesxe2x80x9d to establish the connection.
In xe2x80x9cmaster-slavexe2x80x9d systems, which are usually simple, communication between the xe2x80x9cslavesxe2x80x9d cannot occur directly but rather is possible only via the xe2x80x9cmaster.xe2x80x9d This places a load on the entire bus system over which transmission is occurring, and requires large calculation capacity on the part of the xe2x80x9cmasterxe2x80x9d for forwarding messages.
A method according to the present invention has, in contrast, the advantage that a logical point-to-point connection between components is possible with no need for the information to pass through a designated station. It is thereby possible for messages to be sent directly between two components. Forwarding of messages via the xe2x80x9cmasterxe2x80x9dxe2x80x94as required, for example, in a simple xe2x80x9cmaster-slavexe2x80x9d system for communication between two xe2x80x9cslavesxe2x80x9dxe2x80x94can be eliminated. Any component can initiate connection establishment. The definition of component functions is important not for connection establishment, but rather for maintaining the connection. The definition must, however, be made for all components a priori.
In particular, according to the method further components can easily be added to an existing system, even during operation.
The load placed on the transmission line by the network management system may be regarded as very small.
The definition of the components, which is made a priori, is important for maintaining the connection. If the initiative for connection establishment comes from a component to which, by definition, the monitoring and termination function for that connection was allocated, that component will advantageously continue to maintain the connection.
The initiative for establishment of a connection can just as easily come from a component to which, according to the definition, no monitoring or termination functions for that connection are allocated. In that case the logical component takes over further maintenance of the connection to which the functions for that connection are allocated.
Because of the hierarchical structure, it is possible to perform a subdivision into multiple systems which each comprise a (connection) xe2x80x9cmasterxe2x80x9d with the (connection) xe2x80x9cslavesxe2x80x9d allocated to it. In this connection it is possible on the one hand to operate a subsystem of this kind in xe2x80x9cstand-alonexe2x80x9d fashion, i.e. without all the other components. It is possible on the other hand to implement largely autonomous subnetworks which xe2x80x9ccoexist,xe2x80x9d almost without mutual influence, in terms of overall data traffic and network management.
Advantageously, connection establishment is initialized by sending identifiers.
In order to maintain the logical connections, it is advantageous if cyclical telegrams are sent out. The sending of test telegrams is advantageous as a way to check physical connections.
The component according to the present invention has the advantage that the component has a program which allows it to act both as a secondary component in one connection and as a main component in another connection.
Advantageously, the configuration data of the system are stored in nonvolatile memories, so that the overall network can be established more completely after a restart. The storage of configuration data can also be used for error detection and localization.
The components have circuits which allow a reduction in the operating state, for example into sleep mode. This operating state is attained if the cyclical telegram of the main component is absent.